Patients with rheumatoid arthritis unresponsive to conventional therapies will be offered participation in a double-blind therapeutic trial. They will be randomized to two treatment protocols comparing the effects of lymphocyte depletion (lymphapheresis) and plasma removal (plasmapheresis) on rheumatoid synovitis. The disease activity will be monitored by an Articular Index. The risks and benefits of each treatment will be evaluated and compared at the end of 5 weeks of therapy and through a 6 to 12 month follow-up period.